Liposome preparations consist of artificial spherical vesicles whose main chemical components are phospholipids and cholesterol organised in two layers. The process of forming this bilayer is known as sonication. Based on the structure, the vesicles may be classified as either multilammellar or unilamellar. The former have several bilayers while the latter has just a single bilayer. Most vesicles measure less than 400nm in diameter.
One of the methods used in forming the vesicles is known as sonication. Here, the lipid suspension containing cholesterol and phospholipids is hydrated and made to swell so as to separate the various bilayers. As the bilayers separate, they form large lipid vesicles. These are later broken down into smaller units by use of an instrument known as a sonicator. The sonicator delivers high levels of energy to the large molecules and breaks them down within 5 to 10 minutes.
Another technique that may be used is known as extrusion. In this technique, the suspension is first subjected to cyclical freezing and thawing. The aim of this is to improve the homogeneity in the size of the final vesicles obtained. The other alternative is to pass the vesicles through a series of progressively decreasing pores. The large particles are gradually decreased in size and they become smaller and finer.
A number of factors are known to cause a variation in the size of vesicles. These include among others, the duration for which the vesicles are processed, the amount of energy applied, composition and proportion of the lipids and the the tuning of the sonicator. The vesicles have a lot of similarities with cell membranes due to the presence of phospholipids and cholesterol. Both have a hydrophobic and hydrophilic ends.
The uses of lipid vesicles continue to increase by the day. Clinically, they play a central role in the delivery of drugs to various targets. They are now widely preferred over viral vectors for a number of reasons. One of the greatest advantages that they have is the fact that they are not immunogenic and rarely cause allergic reactions. This has been a big problem with the viral vectors. Another significant strength is that they are easier to synthesise and put to use.
The available drug formulations are used in the treatment of a wide variety of disease processes. The drugs include cytarabine (an anticancer agent), liposomal amphotericin B, a highly potent antifungal agent, liposomal IRIV vaccine, morphine and doxorubicin among others. Many other drug formulations are in different phases of clinical trials.
Apart from drug delivery, lipid vesicles also play a vital role in the administration of nutrients. They are especially useful in supplementing nutrients that are deficient in the diet or those that cannot be easily absorbed orally due to their low bioavailability. Liposome encapsulation is currently one of the most efficient ways of administering vitamin C. The same principle is employed in the delivery of pesticides to plants, delivery of enzymes to their sites of action in the body and in the fixing of dyes to textiles.
The vesicles have many other uses most of which are yet to be approved for routine use. A major advantage of liposome preparations is that there are very few serious side effects that have been identified. One of them is the fact that there is a potential to cause cellular toxicity especially when taken in very large quantities or for a prolonged period of time. There are also some concerns regarding the presence various lipid inhibitors in serum.
One of the methods used in forming the vesicles is known as sonication. Here, the lipid suspension containing cholesterol and phospholipids is hydrated and made to swell so as to separate the various bilayers. As the bilayers separate, they form large lipid vesicles. These are later broken down into smaller units by use of an instrument known as a sonicator. The sonicator delivers high levels of energy to the large molecules and breaks them down within 5 to 10 minutes.
Another technique that may be used is known as extrusion. In this technique, the suspension is first subjected to cyclical freezing and thawing. The aim of this is to improve the homogeneity in the size of the final vesicles obtained. The other alternative is to pass the vesicles through a series of progressively decreasing pores. The large particles are gradually decreased in size and they become smaller and finer.
A number of factors are known to cause a variation in the size of vesicles. These include among others, the duration for which the vesicles are processed, the amount of energy applied, composition and proportion of the lipids and the the tuning of the sonicator. The vesicles have a lot of similarities with cell membranes due to the presence of phospholipids and cholesterol. Both have a hydrophobic and hydrophilic ends.
The uses of lipid vesicles continue to increase by the day. Clinically, they play a central role in the delivery of drugs to various targets. They are now widely preferred over viral vectors for a number of reasons. One of the greatest advantages that they have is the fact that they are not immunogenic and rarely cause allergic reactions. This has been a big problem with the viral vectors. Another significant strength is that they are easier to synthesise and put to use.
The available drug formulations are used in the treatment of a wide variety of disease processes. The drugs include cytarabine (an anticancer agent), liposomal amphotericin B, a highly potent antifungal agent, liposomal IRIV vaccine, morphine and doxorubicin among others. Many other drug formulations are in different phases of clinical trials.
Apart from drug delivery, lipid vesicles also play a vital role in the administration of nutrients. They are especially useful in supplementing nutrients that are deficient in the diet or those that cannot be easily absorbed orally due to their low bioavailability. Liposome encapsulation is currently one of the most efficient ways of administering vitamin C. The same principle is employed in the delivery of pesticides to plants, delivery of enzymes to their sites of action in the body and in the fixing of dyes to textiles.
The vesicles have many other uses most of which are yet to be approved for routine use. A major advantage of liposome preparations is that there are very few serious side effects that have been identified. One of them is the fact that there is a potential to cause cellular toxicity especially when taken in very large quantities or for a prolonged period of time. There are also some concerns regarding the presence various lipid inhibitors in serum.
